How can i use blob storage from an azure function in Java

Question

I have an http triggered azure function (written in Java) in which I want to access Blob storage. The code compiles under maven, but when I run it locally and send a post from CURL, the runtime crashes due to a ClassNotFound exception caused by missing com.microsoft.azure.storage.CloudStorageAccount. azure-storage (version 6.0.0) is listed as a dependency in the POM file. Where should the related .jar files be so that they are seen by the function?

Any insights regarding Java azure functions would be appreciated.

Answer 1

According to your needs,I suggest you following this official tutorial to create,run and deploy your java azure function.

Function Class:

package com.fabrikam.functions;

import com.microsoft.azure.serverless.functions.annotation.*;
import com.microsoft.azure.serverless.functions.ExecutionContext;

import com.microsoft.azure.storage.*;
import com.microsoft.azure.storage.blob.*;

/**
 * Hello function with HTTP Trigger.
 */
public class Function {

    // Configure the connection-string with your values
    public static final String storageConnectionString =
            "DefaultEndpointsProtocol=http;" +
                    "AccountName=***;" +
                    "AccountKey=***";

    @FunctionName("hello")
    public String hello(@HttpTrigger(name = "req", methods = {"get", "post"}, authLevel = AuthorizationLevel.ANONYMOUS) String req,
                        ExecutionContext context) {

        try {
            // Retrieve storage account from connection-string.
            CloudStorageAccount storageAccount = CloudStorageAccount.parse(storageConnectionString);

            // Create the blob client.
            CloudBlobClient blobClient = storageAccount.createCloudBlobClient();

            // Get a reference to a container.
            // The container name must be lower case
            CloudBlobContainer container = blobClient.getContainerReference(req);

            // Create the container if it does not exist.
            container.createIfNotExists();

            return String.format("Hello, I get container name : %s!", container.getName());

        } catch (Exception e) {
            // Output the stack trace.
            e.printStackTrace();
            return "Access Error!";
        }
    }
}

Pom.xml：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.fabrikam.functions</groupId>
    <artifactId>fabrikam-functions</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>Azure Java Functions</name>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <functionAppName>fabrikam-functions-20171017112209094</functionAppName>
    </properties>

    <dependencies>
        <dependency>
            <groupId>com.microsoft.azure</groupId>
            <artifactId>azure-functions-java-core</artifactId>
            <version>1.0.0-beta-1</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/com.microsoft.azure/azure-storage -->
        <dependency>
            <groupId>com.microsoft.azure</groupId>
            <artifactId>azure-storage</artifactId>
            <version>6.0.0</version>
        </dependency>

        <!-- Test -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <pluginManagement>
            <plugins>
                <plugin>
                    <artifactId>maven-resources-plugin</artifactId>
                    <version>3.0.2</version>
                </plugin>
                <plugin>
                    <groupId>com.microsoft.azure</groupId>
                    <artifactId>azure-functions-maven-plugin</artifactId>
                    <version>0.1.4</version>
                </plugin>
            </plugins>
        </pluginManagement>

        <plugins>
            <plugin>
                <groupId>com.microsoft.azure</groupId>
                <artifactId>azure-functions-maven-plugin</artifactId>
                <configuration>
                    <resourceGroup>java-functions-group</resourceGroup>
                    <appName>${functionAppName}</appName>
                    <region>westus2</region>
                    <appSettings>
                        <property>
                            <name>FUNCTIONS_EXTENSION_VERSION</name>
                            <value>beta</value>
                        </property>
                    </appSettings>
                </configuration>
                <executions>
                    <execution>
                        <id>package-functions</id>
                        <goals>
                            <goal>package</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <artifactId>maven-resources-plugin</artifactId>
                <executions>
                    <execution>
                        <id>copy-resources</id>
                        <phase>package</phase>
                        <goals>
                            <goal>copy-resources</goal>
                        </goals>
                        <configuration>
                            <overwrite>true</overwrite>
                            <outputDirectory>${project.build.directory}/azure-functions/${functionAppName}
                            </outputDirectory>
                            <resources>
                                <resource>
                                    <directory>${project.basedir}</directory>
                                    <includes>
                                        <include>host.json</include>
                                        <include>local.settings.json</include>
                                    </includes>
                                </resource>
                            </resources>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>

    </build>

</project>

Then use command mvn clean package to pack your maven project into a jar package.

use command mvn azure-functions:run to run your azure function locally.

---

Update Answer:

I ran my azure function and reproduce the same exception as you said.

java.lang.NoClassDefFoundError: com/microsoft/azure/storage/CloudStorageAccount

Exception:
Stack: java.lang.reflect.InvocationTargetException
[10/25/2017 2:48:44 AM]         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[10/25/2017 2:48:44 AM]         at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[10/25/2017 2:48:44 AM]         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)[10/25/2017 2:48:44 AM]         at java.lang.reflect.Method.invoke(Method.java:498)
[10/25/2017 2:48:44 AM]         at com.microsoft.azure.webjobs.script.broker.JavaMethodInvokeInfo.invoke(JavaMethodInvokeInfo.java:19)
[10/25/2017 2:48:44 AM]         at com.microsoft.azure.webjobs.script.broker.JavaMethodExecutor.execute(JavaMethodExecutor.java:34)
[10/25/2017 2:48:44 AM]         at com.microsoft.azure.webjobs.script.broker.JavaFunctionBroker.invokeMethod(JavaFunctionBroker.java:40)
[10/25/2017 2:48:44 AM]         at com.microsoft.azure.webjobs.script.handler.InvocationRequestHandler.execute(InvocationRequestHandler.java:33)
[10/25/2017 2:48:44 AM]         at com.microsoft.azure.webjobs.script.handler.InvocationRequestHandler.execute(InvocationRequestHandler.java:10)
[10/25/2017 2:48:44 AM]         at com.microsoft.azure.webjobs.script.handler.MessageHandler.handle(MessageHandler.java:41)
[10/25/2017 2:48:44 AM]         at com.microsoft.azure.webjobs.script.JavaWorkerClient$StreamingMessagePeer.lambda$onNext$0(JavaWorkerClient.java:84)
[10/25/2017 2:48:44 AM]         at java.util.concurrent.ForkJoinTask$AdaptedRunnableAction.exec(ForkJoinTask.java:1386)
[10/25/2017 2:48:44 AM]         at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
[10/25/2017 2:48:44 AM]         at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
[10/25/2017 2:48:44 AM]         at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
[10/25/2017 2:48:44 AM]         at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
[10/25/2017 2:48:44 AM] Caused by: java.lang.NoClassDefFoundError: com/microsoft/azure/storage/CloudStorageAccount
[10/25/2017 2:48:44 AM]         at com.fabrikam.functions.Function.hello(Function.java:26)
[10/25/2017 2:48:44 AM]         ... 16 more
[10/25/2017 2:48:44 AM] Caused by: java.lang.ClassNotFoundException: com.microsoft.azure.storage.CloudStorageAccount
[10/25/2017 2:48:44 AM]         at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
[10/25/2017 2:48:44 AM]         at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
[10/25/2017 2:48:44 AM]         at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
[10/25/2017 2:48:44 AM]         ... 17 more
[10/25/2017 2:48:44 AM] .
[10/25/2017 2:48:44 AM]   Function had errors. See Azure WebJobs SDK dashboard for details. Instance ID is '3450abda-99a0-4d75-add2-a7bc48a0cb51'
[10/25/2017 2:48:44 AM] System.Private.CoreLib: Exception while executing function: Functions.hello. System.Private.CoreLib: Result:

After some research, I found out that it was because the jar packaged without dependent jar packages.

So , I added the snippet of configuration as below into my pom.xml

<plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                    <archive>
                        <manifest>
                            <mainClass>Your main class path</mainClass>
                        </manifest>
                    </archive>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

Then please use command mvn-clean-package and you will see two jar files generated.

One is that it does not contain dependent jar packages, and the second one contains dependent jar packages.

Move the fabrikam-functions-1.0-SNAPSHOT-jar-with-dependencies jar into the path：${project.basedir}/target/azure-functions/${function-app-name}/

For me ,it looks like E:\TestAzureFunction\fabrikam-functions\target\azure-functions\fabrikam-functions-20171017112209094.

Don't forget rename the jar to fabrikam-functions-1.0-SNAPSHOT.

Finally, I run the azure function successfully and get the output result via the url: http://localhost:7071/api/mongo.

In addition, you could refer to this github doc for more configuration details about azure function maven plugin.

Hope it helps you.

Answer 2

Can you share any details on the method and types you are using? To do output bindings you need to use the OutputBinding<T> class with the correct annotation. Here's an example of one I just tested to do similar to what you mentioned:

@FunctionName("hello")
public String hello(
        @HttpTrigger(name = "req", methods = {
                "post" }, authLevel = AuthorizationLevel.ANONYMOUS) String req,
        ExecutionContext context, @BlobOutput(name = "blob", connection = "StorageAccount", path = "test/foo.txt")OutputBinding<String> blob)
        {
    blob.setValue("hello world");
    return String.format("Hello, %s!", req);
}

Notice the @BlobOutput attribute and the OutputBinding type (could be String or byte [], but I believe if doing byte [] you also need to set the dataType to "binary" on the @BlobAttribute.

Let me know if that works